Novel design analysis tools to increase precision and reduce variation in hip replacement performance

Over 60 million patients worldwide suffer from hip osteoarthritis, and increasing numbers of patients are requiring total hip replacement surgery. Although the surgery is highly successful, the ageing active population and rise in obesity are placing extra demands on hip replacements: devices must now withstand higher loads and survive for longer durations in the body. The number of revision surgery procedures to replace worn out or damaged components is rising, and there is a need to develop more robust hip replacement devices that can withstand these increasing demands across all patient groups. One of the major causes of failure of hip replacements is due to wear and fatigue of the device components. These damage processes can increase dramatically if the components are not well aligned relative to each another, or relative to the direction of the loads they experience in the body. There can be many factors which affect the alignment, including the device design and surgical procedure as well as the patient anatomy and biomechanics. In this proposal, we will develop computer models to simulate hip replacement performance under different misalignment conditions. We will incorporate patient and surgical variations into the model so that we can define exactly what levels of alignment are required for specific devices to operate adequately. This will enable us to provide better guidance on the choice of device for individual patients to reduce the likelihood of misalignment. It will also help inform surgeons on the positioning of the components for different patient characteristics. We will work with a major orthopaedic company (DePuy Synthes) to integrate the computer models into their new product development process, so that the next generation of devices can be designed to be more robust to alignment variations, and surgical tools can be developed to help align devices with better precision in the most critical directions. We will also work with regulators and standards agencies to develop new testing requirements that take account of the variations in patients and surgery, so that all new products will have to undergo more robust testing before they are introduced onto the market. In the longer term, the methods we develop will help extend the lifetime and reliability of the next generation of hip replacements and enable these devices to meet the increasing demands of our ageing active population.